KR20100022976A - Membrane filter unit - Google Patents

Abstract

A membrane filter unit that ensures the durability of hollow fiber membrane module through prevention of, in activated sludge treatment, bundling of porous hollow fiber membranes of the hollow fiber membrane module by hair, fiber, paper piece, etc. contained in wastewater or entwining or getting stuck thereof between hollow fiber membranes and surrounding frame member, etc. The membrane filter unit (5) includes hollow fiber membrane module (9) composed of multiple sheetlike hollow fiber membrane elements (10) arrayed in parallel at given intervals, each of the hollow fiber membrane elements (10) obtained by parallel arrangement of a multiplicity of porous hollow fiber membranes (10a). Further, the membrane filter unit (5) includes, disposed inferiorly to the hollow fiber membrane module (9), air diffuser (15) capable of emitting minute bubbles toward the lower end of the hollow fiber membrane module and generating a gas-liquid mixed current vertically swirling between the internal space and external space of the hollow fiber membrane module. Still further, the membrane filter unit (5) includes residual foreign matter removing means capable of generating forced flow in part of the mixed current between porous hollow fiber membranes of the hollow fiber membrane module (9) and between sheetlike hollow fiber membrane elements to thereby expel any residual foreign matter mingled in the gas-liquid mixed current to outside of the hollow fiber membrane module.

Description

Membrane Filtration Unit {MEMBRANE FILTER UNIT}

INDUSTRIAL APPLICABILITY The present invention is applied to an activated sludge treatment method in which organic matter and debris contained in industrial wastewater or domestic wastewater, or wastewater containing microorganisms and bacteria are biochemically treated and solid-liquid separation is performed using a separation membrane. Membrane filtration unit.

A denitrification method in a wastewater treatment method, wherein the sludge is disposed between an aerobic tank in which molecular oxygen is not present and an aeration tank which releases air from an air diffuser in the sludge. The activated sludge circulating variation which circulates, oxidizes ammonia nitrogen to nitrate nitrogen in an aeration tank, reduces nitrate nitrogen in an oxygen-free tank, and discharges it out of the system as nitrogen gas is conventionally widely performed. However, according to this method, although nitrogen can be removed efficiently, phosphorus cannot be removed sufficiently. This is because the anaerobic anaerobic tank does not sufficiently increase due to dissolved oxygen, nitrate nitrogen, and nitrite nitrogen contained in the circulating water from the aerobic tank, and phosphorus release from phosphorus accumulating bacteria does not occur sufficiently.

For this reason, when it is necessary to perform denitrification and phosphorus removal at the same time, an absolute anaerobic tank containing neither molecular oxygen nor bound oxygen such as nitric acid or nitrous acid is disposed in front of the anoxic tank (denitrification tank) of the activated sludge circulation modification. The so-called A ₂ / O method which denitrifies and dephosphorizes biochemically is used. In the above absolute anaerobic tank, polyphosphoric acid by polyphosphoric acid accumulating bacteria is hydrolyzed to elute phosphorus, and a biochemical oxygen demand (hereinafter referred to as BOD) component is blown into the cells. In order to maintain the absolute anaerobic state, it is required to have a BOD of 50 mg / L or more.

However, this wastewater treatment method using the A ₂ / O method has a problem in that a complete anaerobic tank must be provided in excess as compared to the activated sludge circulation variant, and a large device installation area is also required.

Therefore, for example, WO 03/101896 (Patent Document 1) proposes a wastewater treatment method capable of removing nitrogen and phosphorus without using a flocculant in only two treatment tanks, an oxygen-free tank and an aeration tank. The wastewater treatment method is an active sludge processing apparatus for performing so-called activated sludge circulation transformation, which is configured to circulate sludge between an anaerobic tank and an aeration tank and to treat the wastewater biochemically, and transmits sludge that is a circulating fluid from the aeration tank to an anaerobic tank. The sludge is configured to take out sludge which is a circulating fluid from below the acid generator generating device at the lowest position arranged in the aeration tank, so that DOC (hereinafter referred to as DOC) at the site where sludge is taken out is 0.5 mg / L or less. At the same time, DOC is preferably 0.2 mg / L or less at the site where the sludge fed from the aeration tank enters the anaerobic tank. By doing in this way, only two treatment tanks, an anoxic tank and an aeration tank, can be used to remove both nitrogen and phosphorus without using a flocculant or the like.

By the way, in the aeration tank in this kind of activated sludge treatment, as described in Patent Literature 1, a plurality of sheet-shaped hollow fiber membrane elements using a plurality of porous hollow fibers in parallel are assembled in parallel and assembled. A membrane filtration unit having a hollow fiber membrane module and an acid generator generator, which is disposed below the hollow fiber membrane module and discharges air toward the hollow fiber membrane module, has a biochemical treatment efficiency and filtration of activated sludge. It is used a lot for the reason that efficiency is high.

From the acid generator, a predetermined amount of air is discharged as fine bubbles in the sludge, rises as a gas-liquid mixed flow while raising the sludge, and flows upward through the internal voids of the hollow fiber membrane module, Flow through the desert module flows down the outside of the membrane filtration unit to form a gas-liquid mixed swirl flow. While the gas-liquid mixed swirl flows up and down, the oxygen in the air becomes molecular oxygen, dissolves in the sludge, decomposes organic matters, or nitrifies, and / or blows phosphorus into the polyphosphate accumulating bacteria and grows. The gas-liquid mixed liquid is grown as described in, for example, Japanese Patent Application Laid-Open No. 2000-51672 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2000-84553 (Patent Document 3). The contaminated substance adhering to the hollow fiber membrane element is peeled off and cleaned by so-called air scrubbing which is applied to the structure of the hollow fiber membrane module and vibrated. At this time, the sludge is sucked by the suction pump and the solid-liquid separation is made through the porous hollow fiber membrane, the treated water is sent to the external treatment tank through the hollow portion of the hollow fiber membrane.

Patent Document 1: WO 03/101896

Patent Document 2: Japanese Patent Application Laid-open No. 2000-51672

Patent Document 3: Japanese Patent Application Laid-Open No. 2000-84553

As described in Patent Documents 1 to 3, it is common that the biochemically activated sludge treatment using this kind of hollow fiber membrane module includes an aeration process. As described above, the hollow fiber membrane module parallelly parallels a plurality of porous hollow fiber membranes with a necessary gap, and fixes the entire hollow fiber membrane element through a fixing resin to a rectangular frame member to form a sheet-like hollow fiber membrane element. . The hollow fiber membrane elements are arranged in parallel at intervals of the required number of sheets to form a rectangular hollow fiber membrane module. The gas-liquid mixed swirl flow generated by the air bubbles emitted from the acid generator generating unit disposed below the hollow fiber membrane module is accompanied by turbulent flow by scrubbing the porous hollow fiber membrane.

On the other hand, the sludge to be treated contains various organic matters, such as fibers, seams, hair, and pieces of paper, as well as organic matter. These mixtures are conveyed upward by the gas-liquid mixed swirl flow which flows from below to the hollow fiber membrane module, and are often caught by the structural member of a hollow fiber membrane module. In this case, only the scrubbing action by the gas-liquid mixture flowing through the hollow fiber membrane module by the conventional acid generator generator, in particular, fibers, seams, hair, etc. are caught or adjacent to the frame of the hollow fiber membrane module or the porous hollow fiber membrane itself. It is not possible to prevent entanglement between the porous hollow fiber membranes or between the extraction pipe of the treated water and the porous hollow yarns. When these fibers, seams, hairs, etc., are caught or entangled, not only the hollow fiber membranes are bundled, but also the filtration performance is reduced, and dissolved oxygen does not fall between the hollow fiber membranes so that sludge treatment is not performed smoothly. do. In such a case, the hollow fiber membrane module is pulled out of the aeration tank and taken out of the tank to be replaced by a new hollow fiber membrane module.

The present invention has been made to solve such a problem, the specific object of the active sludge treatment apparatus as described above, the hair, fibers, pieces of paper, etc. contained in the drainage bundles the porous hollow fiber membrane of the hollow fiber membrane module, In order to prevent entanglement or jamming between the hollow fiber membrane and the surrounding frame member or the like, the durability of the hollow fiber membrane module is ensured.

This object is provided with an anaerobic tank and an aerobic tank, which are the basic components of the present invention, and a membrane filtration unit is immersed in the aerobic tank, and the membrane is applied to an activated sludge treatment method in which the wastewater is sequentially biologically separated into active sludge and treated water. A filtration unit, wherein the membrane filtration unit has a plurality of sheet-like hollow fiber membrane elements obtained by arranging a plurality of porous hollow fibers in parallel with a fine gap at a predetermined interval toward the vertical direction. The hollow fiber membrane module arranged in parallel and below the hollow fiber membrane module, and discharges a small bubble toward the lower end of the module, in the vertical direction between the inner space and the outer space of the hollow fiber membrane module It comprises a fine bubble generating section for generating a gas-liquid mixed flow to turn, to the membrane filtration unit Each hollow fiber membrane element of the hollow fiber membrane module of the hollow fiber membrane module has a first region having a small gap between the porous hollow fiber membranes constituting the hollow fiber membrane element and a second region having a wide gap formed between the small gap region. It is effectively achieved by the membrane filtration unit characterized in that.

Partial spacing between a plurality of hollow fiber membrane elements adjacent to the parallel direction of the hollow fiber membrane module is formed wide, it may be characterized in that the obstruction member is disposed in the lower end inlet of the gas-liquid mixture flow of the partial gap. In addition, the membrane filtration unit is disposed so as to surround the periphery of the hollow fiber membrane module and the microbubble generating portion has a wall material opened up and down, and the lower end portion of the wall material is characterized in that it has a skirt portion extending wider bottom There is a case. It is preferable that the extension length of the skirt part in the horizontal direction is 1 mm or more and 1000 mm or less, and the inclination angle with respect to the perpendicular | vertical line extended vertically downward from the lower end part of the said wall material of the skirt part may be 10 degrees or more and 70 degrees or less.

Moreover, both the space | interval between the said hollow fiber membrane element and the clearance gap between the porous hollow fiber membrane which are the structural yarns of the said hollow fiber membrane element may be made uneven simultaneously.

As mentioned above, wastewater and industrial drainage contain fibers, yarns of various materials, paper scraps (non-woven fabrics), and large solids are removed by the screen at the raw water stage. Debris, such as long, flexible and flexible fibers or hair, leaves the screen and mixes with the drainage and enters the treatment tank. In the treatment of waste water, in particular, when the aeration treatment is performed, the residue flows through the gas-liquid mixed stream while flowing to the hollow fiber membrane module. Since this hollow fiber membrane module consists of many porous hollow fiber membranes and the frame which supports it as mentioned above, the said dregs are caught by a porous hollow fiber membrane or a frame, or they are entangled, and bundles a plurality of porous hollow fiber membranes together, do. In addition, residues may become entangled and become a dumpling shape. The effect of such debris is large, for example, to significantly reduce the filtration performance of the hollow fiber membrane element. It is practically difficult to remove the debris from the tank to recover the performance degradation of the hollow fiber membrane element, and to lift out of the tank for each membrane filtration unit and take it out, so that the hollow fiber membrane element in which the debris is entangled must be replaced with a new hollow fiber membrane element. do.

Therefore, in this invention, in order to avoid the above-mentioned problem, the 2nd area | region which made a part of the clearance gap between the several porous hollow fiber membranes which comprise each said hollow fiber membrane element wider than another clearance gap is formed. A part of the gas-liquid mixed flow which flows through the space between the plurality of hollow fiber membrane elements from below and moves upwards moves between the hollow fiber membrane elements across the widely formed gap, and rises between the hollow fiber membrane elements. The turbulence is generated in the stream, and the residue, which is caught or entangled in the first region having a narrow gap, is transported upward and taken out to the outside of the membrane filtration unit. As a result, even after long-term treatment, it is difficult for the hollow fiber membrane element to harden in a dumpling shape, and the lumps of waste are not attached to the hollow fiber membrane element or the like, and the plurality of porous hollow fiber membranes are not bound by the residue. It can withstand the use of organs well.

As described above, as another aspect of the present invention, the above-mentioned debris removal mechanism forms a part of the interval between the hollow fiber membrane elements adjacent to the arrangement direction of the respective hollow fiber membrane modules larger than the other intervals. Thus, for example, it is disclosed also in the said patent document 2 as long as some space | interval between the hollow fiber membrane elements adjacent to the arrangement | positioning direction of a hollow fiber membrane module is simply made larger than another space | interval. However, according to the description of this Patent Document 2, by providing a suitable gap between the sheet-shaped hollow fiber membrane elements, the gas-liquid mixed flow generated by the bubbles from the acid generator is between the hollow fiber membrane elements sandwiching the gap. The large gap of the part will rise quickly. As a result, the hollow fiber membrane element is efficiently scrubbed, and the adsorption of solids onto the membrane surface is suppressed while the filtration operation proceeds.

If the distance between the gaps is too small, a plurality of gas-liquid mixed streams collide with each other and are difficult to move upwards, the scrubbing of the hollow fiber membrane elements is not performed efficiently, and the cleaning effect is lowered, and the distance between the gaps is too large. It is described that the gas-liquid mixed stream rises quickly without resistance, but becomes difficult to contact the hollow fiber membrane element, so that a proper cleaning effect is not obtained.

That is, the large space | interval in patent document 2 is trying to perform filtration operation smoothly, obtaining the moderate upflow of gas-liquid mixture flow, exhibiting an air scrubbing effect, and simultaneously suppressing adsorption of the contaminated substance to a membrane surface. .

On the other hand, in the said aspect of this invention, although coinciding with the said patent document 2 in the point which makes the space | interval between hollow fiber membrane elements larger than another space | interval, in this invention, the waste removal mechanism is between the adjacent hollow fiber membrane elements of the said sheet form. An obstruction member disposed in a portion of the large gap lower end opening formed in the second interposition member is disposed to shield the opening by the interference member, thereby substantially blocking the inflow of gas-liquid mixed flow into the opening. The obstruction member may be made of an elongated plate, and a gap may be provided between the openings. In this case, you may arrange | position the said board | plate material so that gas-liquid mixture flows through the several hollow fiber membrane element adjacent to the said opening.

By this structure, the gas-liquid mixed flow which has risen from below the hollow fiber membrane module is collected toward the hollow fiber membrane elements arranged at regular intervals by the obstruction member, and flows in between the hollow fiber membrane elements. Thus, the gas-liquid mixed flow which flowed in between the hollow fiber membrane elements flows into the large space | interval area formed above the interference | blocking member, changes direction, and flows finely above the space | interval area. By the cross flow and the upward flow at this time, the residue which is going to be stuck to a porous hollow fiber membrane or a hollow fiber membrane element, and the residue which is going to harden to a tip shape are carried out from a hollow fiber membrane module to the exterior. In this way, the debris flowing between the hollow fiber membrane elements is intended to be caught by the porous hollow fiber membrane, but a large gap formed above the interfering member accompanied by debris flowing across the hollow fiber membrane is intended to be caught by the hollow fiber membrane. It is conveyed to an area | region and burns the said gap area | region in the flow which rises rapidly upwards, and flows out of a hollow fiber membrane module rapidly.

A conventional membrane filtration unit is surrounded by a wall material whose upper and lower sides are surrounded by the hollow fiber membrane module and the side periphery of the acid generator generator disposed below it. Bubbles generated from the acid generator are raised to form a mixed flow with sludge. This mixed flow rises through the hollow fiber membrane module of the membrane filtration unit, flows out of the upper surface opening of the unit, and is lowered from the upper side to the lower side of the unit, and then discharged from the diffuser generator from the bottom opening of the unit. It joins with the upward flow which arises by a bubble, raises the inside of a membrane filtration unit, and repeats this, and produces the swirl flow which circulates up and down inside and outside of a membrane filtration unit.

As in still another representative embodiment of the present invention, when the lower end portion of the wall member is provided with a skirt portion extending downward, the periphery of the wall member of the membrane filtration unit in the above-described gas-liquid mixed swirl flows downward from above. The downward flow flowing toward the surface widens in the shape of the end portion gradually spreading in the skirt portion, but at the same time, it is attracted to the central portion of the bottom opening of the membrane filtration unit by the gas-liquid mixed upward flow generated by the bubbles discharged from the acid generator. It is pulled out and flows upward, and a lot of gas-liquid mixing flow volume flows in into the hollow fiber membrane module of a membrane filtration unit rather than when there is no skirt part, and it flows in.

Therefore, the flow velocity which passes through the inside of a hollow fiber membrane module increases, and the waste which tries to be caught by the component member of this module flows upwards with the said mixed flow by the flow rate of a gas-liquid mixed flow, and conveys it to the exterior of a membrane filtration unit. do. Therefore, it is hard to bind the plurality of porous hollow fiber membranes or attach them to the hollow fiber membrane elements, so that the particles caught in the constituent members of the membrane filtration unit or hardened into a tip-like shape rarely occur. Guaranteed. Moreover, when the extension length of the said skirt part is shorter than 1 mm, the dense amount of gas-liquid mixture flow will become too small, and the flow volume of the grade which excludes waste is not obtained. Moreover, when it exceeds 1000 mm, the flow volume of the surrounding gas-liquid mixture flow which is going to aggregate is too large, and only the upstream of the gas-liquid mixture flow by the rise of the bubble which arises from an acid generator can not fully aggregate the flow volume around them, Rather, the flow rate passing through the inside of the hollow fiber membrane module does not reach the flow rate enough to carry the residue, so that poor filtration due to the residue is likely to occur. Moreover, when the inclination angle with respect to the perpendicular | vertical line extended vertically downward from the lower end part of the said wall material of the said skirt part is less than 10 degrees, the density | concentration of gas-liquid mixture flow is small, and it becomes a result which hardly changes with the conventional. In addition, when it exceeds 70 degrees, since the said downflow will spread in all directions, what is called a turning flow will not arise.

1 is a schematic diagram of a structure of a membrane separation activated sludge treatment apparatus to which the membrane filtration unit of the present invention is applied.

2 is a three-dimensional view showing a part of the entire structure of a conventional membrane filtration unit broken.

It is a perspective view which shows typically the structural example of the hollow fiber membrane element which is a structural member of a hollow fiber membrane module.

4 is a three-dimensional view showing an example of a hollow fiber membrane module that is one of the constituent members of the membrane filtration unit as the first embodiment of the present invention.

5 is a three-dimensional view of an acid generator generator that is one of the constituent members of the membrane filtration unit.

Fig. 6 is a three-dimensional view schematically showing an example of the hollow fiber membrane module as the second embodiment of the present invention.

7 is an external view schematically showing the membrane filtration unit as a third embodiment of the present invention.

[Description of the code]

1: fine eye screen

2: raw water adjustment tank

3: anoxic tank

4: aeration tank

5: membrane filtration unit

6: extraction site of circulating fluid

7: treatment tank

8: sludge storage tank

9: hollow fiber membrane module

10: hollow fiber membrane element

10a: hollow fiber membrane

10g: hollow fiber membrane element group

11: membrane sheet

11a: potting material

12: filtered water outlet tube

12a: filtered water outlet

12b: L type joint

13: lower frame

14: vertical lever

15: acid generator

16: air inlet pipe (branch pipe)

17: diffuser

18: air supervision

19: on-off valve

20: upper wall material

21: catchment header tube

21a: catchment

21b: L type joint

21c: water inlet

22: suction pipe

22a: branch line

23: on-off valve

24: lower wall material (skirt portion)

24a: support column

28: plate (drag removal mechanism)

P1: first liquid pump

P2: second liquid pump

Pv: Suction Pump

A: 1st area | region (fine clearance area | region)

B: second area (area of large gap)

C: aeration blower

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described concretely based on a representative Example, referring drawings.

1 shows an example of a schematic structure of an activated sludge treatment apparatus to which the membrane filtration unit of the present invention is applied.

According to this activated sludge processing apparatus, the waste water (raw water) from which the relatively large solid content was removed by the fine eye screen 1 is introduced into the raw water adjustment tank 2. In this case, the liquid level is measured by a liquid level meter (not shown), and the first liquid feeding pump P1 is intermittently operated to adjust the liquid level in the tank within a predetermined range. The raw water sent by the first liquid pump P1 is introduced into the oxygen-free tank 3 and then flows into the adjacent aeration tank 4 using the raw water flowing from the oxygen-free tank 3. In this aeration tank 4, the membrane filtration unit 5 of many groups is immersed and arrange | positioned. The treated water which has just been separated into the activated sludge and the treated water by this membrane filtration unit 5 is fed to the treated water tank 7 by the suction pump Pv. On the other hand, solid content (suspension material) of the sludge aerated by the aeration tank 4 and grown is settled to the tank bottom by its own weight, and the surplus sludge is stored in the sludge storage tank 8. In addition, a part of sludge inside the aeration tank 4 is conveyed to the anoxic tank 3 by the 2nd liquid feed pump P2, and it circulates.

According to this membrane separation activated sludge treatment apparatus, raw water is biologically purified by activated sludge in the oxygen-free tank 3 and the aeration tank 4. The nitrogen is removed by a so-called nitriding denitrification reaction by circulating sludge between the anoxic tank 3 and the aeration tank 4. The organic substance converted into BOD (biochemical oxygen demand) is oxidatively decomposed and decomposed by the air discharged from the air discharge portion of the membrane filtration unit 5 which is mainly an aeration apparatus disposed in the aeration tank 4. Phosphorus removal is carried out by blowing into the body of microorganisms as polyphosphoric acid by the action of microorganisms (phosphorus accumulation bacteria) in sludge. The microorganisms take in phosphorus in aerobic state and release phosphorus accumulated in the body in anaerobic state. Phosphorus accumulating bacteria absorb more phosphorus in an aerobic state than the amount of phosphorus released in the anaerobic state when repeatedly exposed to anaerobic and aerobic conditions.

Some nitrogen compounds, such as feces and dead bodies derived from living organisms, are assimilated into plants and bacteria as fertilizers. In addition, some of these nitrogen compounds are oxidized to nitrous acid and nitric acid by independent nutrient ammonia oxidizing bacteria or independent nitrite oxidizing bacteria under oxygen-rich aerobic conditions. On the other hand, under anaerobic conditions without oxygen, microorganisms called denitrification bacteria produce nitrous acid from nitric acid instead of oxygen, and further reduce to dinitrogen monoxide and nitrogen gas. This reduction reaction is called the said nitriding denitrification reaction.

The circulation of the sludge between the anoxic tank 3 and the aeration tank 4 is not necessarily limited to which of the tanks are to be fed using the pump, but is usually anoxic tank from the aeration tank using the second liquid feed pump P2. The liquid is fed into (3), and flowed into the aeration tank 4 by the flow overflowing from the oxygen-free tank 3. In this embodiment, DOC in the site | part where the circulating fluid from the aeration tank 4 enters the anoxic tank 3 is 0.2 mg / L or less, and / or DOC of the site | part which takes out a circulating fluid from the aeration tank 4 By setting it to 0.5 mg / L or less, the inflow of dissolved oxygen into the oxygen-free tank 3 is suppressed and the anaerobic in the oxygen-free tank 3 is sufficiently maintained, thereby promoting the release of phosphorus.

If substantially no dissolved oxygen, nitrate ions, or nitrite ions are present in the oxygen-free tank 3, organic matter is anaerobicly decomposed, and polyphosphoric acid accumulated in the bacteria is released out of the cells as phosphoric acid. In this embodiment, it is preferable that the DOC in the site | part returned from the aeration tank 4 to the oxygen-free tank 3 shall be 0.2 mg / L or less, and when it is 1 mg / L or less, phosphorus removal property is more stable, Moreover, when it is 0.05 mg / L or less, since it stabilizes more, it is preferable. In addition, the measurement of DOC can be measured using the normal DO system by a diaphragm electrode method.

In order to make DOC of the site | part 6 which draws out a circulating fluid (sludge) from the aeration tank 4 to 0.5 mg / L or less, the site | part which takes out sludge from the aeration tank 4 into an anaerobic tank 3 is made into the retention part of sludge. It is preferable. Retention part of sludge means the site | part which is hard to be influenced by the flow of sludge by aeration. For example, when a space is provided between the membrane filtration unit 5 and the bottom of the aeration tank 4, sludge present in the lower portion of the membrane filtration unit 5 is not stirred well, and thus becomes a retention portion.

Therefore, as shown in FIG. 1, the sludge is taken out from the lower part than the position of the membrane filtration unit 5, so that DOC of the site | part 6 which takes out the circulating fluid (slow) from the aeration tank 4 shall be 0.5 mg / L or less. can do. In addition, when the several membrane filtration unit 5 is arrange | positioned in parallel in the aeration tank 4, the site | part which takes out a circulating fluid (sludge) is made below the aeration apparatus. Further, the distance from the membrane filtration unit 5 to the portion from which the sludge is taken out is preferably spaced 20 cm or more downward, more preferably 30 cm or more.

The flow of sludge in the aeration tank 4 mainly rises with the rise of bubbles from the air outlet of the air in the aeration portion by the membrane filtration unit 5, and the sludge in the portion that is not aerated. It descends and the whole is stirred by this. At this time, if the oxygen utilization rate rr of the sludge in the aeration tank 4 is kept high, oxygen is rapidly consumed in the portion that is not aerated, and thus it is easy to form a portion where the dissolved oxygen is lowered in the aeration tank 4. Here, the oxygen utilization rate (rr) of the sludge in the aeration tank 4 means the oxygen utilization rate of the sludge taken from the aerated part of the aeration tank 4, and the measuring method is a sewage test method (1997, a corporation) It is available according to the Japan Sewerage Association).

2 shows a representative example of a conventional membrane filtration unit 5. As shown in FIG. 2, the membrane filtration unit 5 includes a hollow fiber membrane module 9 fixed in parallel with a plurality of hollow fiber membrane elements 10 arranged in a vertical direction with a hollow fiber membrane longitudinal direction, and the hollow fiber membrane A diffuser generator 15 is disposed below the module 9 at intervals of the required amount. The hollow fiber membrane element 10 communicates and supports the open end of the upper end of the hollow fiber membrane sheet 11 in which a plurality of porous hollow fiber membranes 10a are parallel to the filtrate extraction pipe 12 through the potting material 11a. At the same time, the lower end is blocked and fixedly supported by the lower frame 13 through the potting material 11a, and a pair of longitudinal levers 14 at each end of each of the filtered water outlet pipe 12 and the lower frame 13 are provided. It is supported by the structure. A plurality of hollow fiber membrane elements 10 are accommodated and supported in parallel in almost the entire volume of the rectangular tubular upper wall material 20 whose upper and lower end faces are open with the sheet surface vertical.

Here, the hollow fiber membrane element 10 is generally arranged in parallel on the same plane with a plurality of porous hollow fiber membranes having the same gap as shown in Fig. 2, but in this embodiment, Figs. As shown in FIG. 4, after forming the 1st area | region which arrange | positioned the said predetermined | prescribed predetermined number with a microgap, the said porous hollow fiber membrane 10a is the same across the 2nd area | region which has a larger gap than the said gap. After forming the 1st area | region which arranged the number of porous hollow fiber membranes 10a with the same microgap, the 2nd area | region which has a big gap is formed, and this is characterized by repeating this. The large gap constitutes a debris removal mechanism for removing debris such as fibers, fiber yarns, and pieces of paper in the present invention.

In this embodiment, the hollow hollow fiber 10a is a hollow hollow fiber of PVDF (polyvinylidene fluoride) which is hollow in the longitudinal direction along the central portion thereof, and the pore diameter of the filtration hole is 0.4 mu m. The effective film area per sheet is 25 m 2. The sheet-shaped hollow fiber membrane element 10 is 20 sheets per membrane filtration unit 5, the size of which is 30 mm in depth, 1250 mm in width, and the lower frame 13 from the upper surface of the filtered water outlet tube 12. The length up to the bottom surface of is 2000 mm. The size of the one-membrane filtration unit 5 which also included the diffuser generator 15 is 1552.5 mm in depth, 1447 mm in width, and 3043.5 mm in height. The length of the said filtered water extraction pipe 12 is 1280 mm, the material is ABS resin, and the material of the vertical lever 14 is SUS304. In addition, in the example of illustration, the total number of the porous hollow fiber membranes 10a arrange | positioned between the filtrate water extraction pipe 12 and the lower frame 13 is 1575 pieces, and these are divided into three, as shown in FIG. 3, and 525 pieces. Each second region having two large gaps is formed. This large gap is set to 20 mm.

However, materials such as the porous hollow fiber membrane 10a, the filtered water extraction pipe 12, and the longitudinal lever 14, the size of the hollow fiber membrane element 10, the size of the single membrane filtration unit 5, and the hollow fiber membrane per unit The number of elements 10 and the like can be variously changed depending on the use. For example, in terms of the number of hollow fiber membrane elements 10, 20, 40, 60,... It is possible to set arbitrarily, or to the material of the porous hollow fiber membrane 10a, conventionally known ones such as cellulose, polyolefin, polysulfone, polyvinyl alcohol, polymethyl methacrylate, polyfluorinated ethylene can be applied. Can be.

At one end of the filtered water outlet tube 12 of each hollow fiber membrane element 10, a outlet 12a of the high quality treated water filtered by each porous hollow fiber membrane 10a is formed. In this embodiment, the L-shaped joints 12b are mounted in liquid-tight manner through the sealing member in the same manner as the membrane filtration unit 5 shown in FIG. 2 in each outlet 12a. In addition, a collecting header tube 21 is provided horizontally along an end edge of the side where the outlet 12a of the upper end of the upper wall 20 is formed. In this water collecting header tube 21, water collecting holes 21a are formed at positions corresponding to the plurality of air outlets 12a, respectively, and L-shaped joints 21b which are the same as the air outlet 12a in each water collecting port 21a. Is mounted liquid tightly through the sealant. The treated water outlet 12a of the filtered water outlet pipe 12 and the catchment port 21a of the catchment header tube 21 are connected to each other so as to be connected to each other by connecting the L-shaped joints 12b and 21b mounted thereon. . One end of the collecting header tube 21 is provided with a water supply port 21c connected to the suction pump Pv and the suction pipe line 22. As shown in FIG. 1, the water supply port 21c and the suction pipe line 22 formed for each collection header tube 21 are opened and closed interposed in the branch pipe line 22a branched from the suction pipe line 22, respectively. It is connected via a valve 23.

On the other hand, as shown in FIG. 5, the diffuser generator 15 is formed of a rectangular cylinder having the same upper and lower openings coupled to the lower end of the upper wall material 20, and is downward from the lower end of the four corners. It is accommodating and fixed to the bottom of the lower wall material 24 provided with four support pillars 24a which extend. The diffuser generator 15 is installed horizontally along the front side inner wall surface of the lower wall member 24 in the width direction, and is connected to a blower B arranged outside, via a pipe. The air inlet pipe (branch line) 16 to be connected and the air inlet pipe (branch line) 16 are arranged at a predetermined interval in the longitudinal direction, and one end is fixedly installed and the other end is located on the rear side. It has a plurality of diffusers 17 fixed horizontally along the inner wall surface. An end portion of the diffuser 17 connected to the air inlet pipe (branch pipe) 16 communicates with the inside of the air inlet pipe (branch pipe) 16, and the other end of the diffuser pipe 17 is Occluded

According to the example of illustration, the main body of this diffuser 17 is comprised from the rubber tube to which the slit was provided, The slit which is not shown in figure which communicates in and out along the longitudinal direction is formed in the lower surface arrange | positioned horizontally. The diffuser generator 15 is preferably disposed at intervals of 45 cm downward from the lower end of the hollow membrane element 10, and protrudes the support pillar 24a downward from the lower wall material 24, Exposure to the outside is desirable to facilitate the flow of sludge. At this time, in order to make DOC of the site | part which removes a circulating fluid (sludge) from the aeration tank 4 into 0.5 mg / L or less, the distance from the membrane filtration unit 5 to the site | part which removes sludge as mentioned above was mentioned above. It is preferable to space apart 20 cm or more downward, and it is more preferable to space 30 cm or more. In addition, the diffuser generator 15 which concerns on a present Example is arrange | positioned correspondingly for every several membrane filtration unit 5, and the air sent from the same aeration blower C to each diffuser generator 15 is carried out. An air inlet pipe (branch pipe) 16 having an air main pipe 18 directly connected to the aeration blower C, for separating, from the air main pipe 18 to each of the acid generator generators 15. Connected via

Like the membrane filtration unit of the illustrated example having the above configuration, in the hollow fiber membrane element 10, a predetermined number of porous hollow fiber membranes 10a have a small gap between the first regions A of the fine gaps in parallel. Even in the case where a plurality of second regions B having a large gap S are provided in the air, the gas-liquid mixed flow with sludge that rises with the fine bubbles discharged from the acid generator generator 15 is contained in the membrane filtration unit 5. Infiltrating into the inner space of the hollow fiber membrane module 9, the fibers and hairs mixed in the gas-liquid mixture flow, or debris such as fiber thread or pieces of paper also invade the inner space of the hollow fiber membrane module 9 .

In this case, when the hollow fiber membrane elements are configured in parallel with all the hollow hollow fiber membranes having the same minute gap as in the prior art, the residues infiltrated into the hollow fiber membrane module 9 are porous hollow fiber membranes, lower frames, and filtered water outlet tubes 12 Or the like, and a plurality of porous hollow fiber membranes are tightly bound together, or they are often attached to the membrane surface of the hollow fiber membrane element 10 in a state where the debris gathers and is entangled with each other and hardened into a tip shape. This is because the gas-liquid mixed flows introduced between the membrane elements in the hollow fiber membrane module 9 have a relatively large space, so that the flow rate is large, and most of them flow upward toward the upper portion of the hollow fiber membrane module 9 as the upward flow. Debris mixed into the gas-liquid mixed solution is often caught in the filtered water outlet tube 12 or the like at the upper end. On the other hand, the gas-liquid mixed stream flowing in a small space between adjacent porous hollow fiber membranes also has a small flow in the transverse direction in the first region A having a minute gap, and furthermore, scrubbing between adjacent porous hollow fiber membranes is performed. Due to the vibration caused by the turbulence, the debris mixed into the gas-liquid mixed liquid moves in an undirected flow and is caught by any one of the surrounding porous hollow fiber membranes. While this overlaps, it entangles with the surrounding porous hollow fiber membrane, and bundles a some porous hollow fiber membrane tightly.

In this way, when a plurality of porous hollow fiber membranes (10a) are caught by the wastes, the respective hollow fiber membranes (10a) are strongly adhered to each other, and the filtration holes of the hollow fiber membranes are blocked. It will leak out. In addition, as mentioned above, when a lump of waste arises and adheres to a membrane surface, the eye of the filtration hole of a hollow fiber membrane is similarly blocked, and the filtration performance will fall remarkably.

On the other hand, according to the example of illustration, although the space of the 2nd area | region B with a large space | interval between adjacent hollow fiber membrane elements 10 tries to raise | generate a large flow like a conventional thing, each hollow fiber membrane element 10 Since the predetermined number of porous hollow fiber membranes 10a form the second region B of the large gap between the first regions A in parallel with a small gap, the hollow fiber membrane element ( The flow is changed so as to traverse a large amount of streams trying to flow a large space upward between 10) in a diagonally upward direction across the second region B of the large gap formed between the first regions A. As a result, the turbulence generated in the first region A is attracted toward the flow transversely above the inclination, thereby creating a flow across each porous hollow fiber membrane 10a. As a result, for example, the debris which is going to be caught by the porous hollow fiber membrane 10a flows in the same direction through the flow which crosses the said porous hollow fiber membrane 10a, and it does not get caught by the porous hollow fiber membrane 10a. Therefore, the filter hole of the porous hollow fiber membrane 10a is not blocked by the influence of the debris, thereby enabling the long-term use of the membrane filtration unit 5.

6 illustrates a second exemplary embodiment of the present invention. According to FIG. 6, the space | interval of the hollow fiber membrane element of the hollow fiber membrane module 9 is not equally spaced, but the some space | interval is enlarged similarly to patent document 2, for example. In the present invention, the spacing between some of the hollow fiber membrane elements is made wider than the other spacing, and further, the gas-liquid mixed flow which rises from below is blocked at the lower end opening of the large section made by the wide spacing. The member is arrange | positioned, It is characterized by the above-mentioned.

According to the example of illustration, the board | plate material 28 used as one set of two elongate sheets is employ | adopted as the said obstacle member. In the second embodiment, the pair of plate members 28 is fixedly installed along the opposite end edges of the lower frames 13 of the hollow fiber membrane elements 10 arranged at equal intervals to form a wide gap. . At this time, the opposite end edge of each board | plate material 28 is inclined slightly downward from the fixed installation end edge, and the slight gap is formed between the front-end | tip facing edges.

In the membrane filtration unit 5 of the second embodiment having such a configuration, the gas-liquid mixed streams rising from the lower side of the hollow fiber membrane module 9 toward the lower surface of the hollow fiber membrane module 9 are formed by the pair of plate materials ( 28 is distributed so as to face the adjacent hollow fiber membrane element group 10g, and does not directly invade the space of the wide space formed between the hollow fiber membrane elements 10. FIG. Therefore, the gas-liquid mixed flow which penetrates into the hollow fiber membrane element group 10g adjacent to the said large space | interval space is added to the gas-liquid mixed flow which rises below the said hollow fiber membrane element group 10g, and the said board | plate material 28 The gas-liquid mixed streams distributed by the above are joined.

Thus, the above-mentioned wastes are mixed in the gas-liquid mixed stream which invades each 10 g of hollow fiber membrane element groups. When the gas-liquid mixed stream containing this waste enters each of the hollow fiber membrane element groups 10g, a flow upwardly inclines toward the wide spaced space formed above the plate 28. Therefore, similarly to the first embodiment, debris mixed into the gas-liquid mixture flows to the porous hollow fiber membrane 10a and the membrane surface during the passage, but because the flow is strong, it does not catch the large gap space. It is guided and finally flows upwards and is taken out of the wall of the membrane filtration unit 5 from above the hollow fiber membrane module 9. As a result, similarly to the above embodiment, the filtration hole of the porous hollow fiber membrane 10a is not blocked by the influence of the residue, and the membrane filtration unit 5 can be used for a long time.

Fig. 7 shows the appearance of the membrane filtration unit 5, which is a third exemplary embodiment of the present invention. In this embodiment, as can be easily understood from FIG. 7, the lower wall material 24 arranged around the diffuser generator 15 of the membrane filtration unit 5 forms a skirt portion which is widened downward. . This skirt part constitutes the waste removal mechanism of this invention. The rest of the configuration is not substantially changed from the conventional configuration. Of course, either or both of the configurations of the first and second embodiments may be employed simultaneously.

In this manner, when the lower end of the membrane filtration unit 5 is a skirt portion, the gas-liquid mixed flow in which bubbles flowing downward outside the upper wall material 20 flows along the skirt portion and one end flows in the diffusion direction, but the skirt portion is The excess flow is concentrated inwardly from the edge of the skirt lower end portion which is attracted to the upward flow of the gas-liquid mixture flow generated by the rise of the bubbles discharged from the air diffuser 15 installed at the lower end of the membrane filtration unit 5, Generates a large amount of gas-liquid mixture. This collected upward flow flows into the lower end of the hollow fiber membrane module 9 whose opening area at the lower end is smaller than that of the skirt. As a result, compared with the membrane filtration unit when there is no skirt part, the flow volume which flows upwards inside a hollow fiber membrane module increases, and also the scrubbing effect of the hollow fiber membrane element 10 improves, and it mixes in gas-liquid mixture stream, It is possible to ensure that any debris is moved. As a result, similar to the first and second embodiments, the life of the membrane filtration unit 5 can be extended.

When the length of the skirt is shorter than 1 mm in the horizontal direction, the skirt portion becomes equivalent to that in which the amount of gas-liquid mixed flow is little, and an increase in flow rate that is large enough to exclude debris cannot be expected. Moreover, when it exceeds 1000 mm, the flow volume of the gas-liquid mixture flow around which it is going to aggregate will be too much, and only the upflow of the gas-liquid mixture flow by the rise of the bubble which arises from an acid generator will not be able to fully aggregate the flow volume around them. On the contrary, the gas-liquid mixed stream passing through the inside of the hollow fiber membrane module 9 does not reach the flow rate for reliably transporting the debris out of the module, so that poor filtration due to the debris easily occurs. Moreover, when the inclination angle (alpha) with respect to the perpendicular | vertical line extended vertically downward from the lower end part of the said wall material of the said skirt part is less than 10 degrees, the amount of increase of gas-liquid mixture flow will be small, and will become the result which hardly changes with the conventional. Moreover, if it exceeds 70 degrees, since the said downflow will spread | diffused in all directions, generation | occurrence | production of what is called a swirl flow will extinguish itself, and the mixing action of sludge will fall.

Although the above description has described typical embodiments of the present invention, for example, any of the above-described first to third examples may be employed, but the first to third examples may be appropriately combined. It is also possible to implement, and various changes are possible in the present invention in the equal range of a claim.

Claims (4)

A membrane filtration unit having an anaerobic tank and an aerobic tank, wherein the membrane filtration unit is immersed in the aerobic tank, and applied to an activated sludge treatment method for biologically treating wastewater and separating the activated sludge and the treated water. A hollow fiber membrane module in which a plurality of sheet-like hollow fiber membrane elements obtained by arranging a plurality of porous hollow fibers in parallel with a fine gap are arranged in parallel with the porous hollow fibers at a predetermined interval toward the vertical direction; And a microbubble disposed under the hollow fiber membrane module, emitting microbubbles toward the lower end of the module, and generating a gas-liquid mixture flowing vertically between the inner space and the outer space of the hollow fiber membrane module. It is provided with a generation unit, Each hollow fiber membrane element of the hollow fiber membrane module in the membrane filtration unit has a wide gap between the first region where the gap between the porous hollow fiber membranes forming the hollow fiber membrane element is minute and the minute gap region. A membrane filtration unit, comprising two regions. The method according to claim 1, wherein a part of the spacing between the plurality of hollow fiber membrane elements adjacent to the parallel direction of the hollow fiber membrane module is formed wide, and an obstruction member is arranged at the lower end inlet of the gas-liquid mixture flow at a part of the spacing. Membrane filtration unit. The said membrane filtration unit is a wall material arrange | positioned so that the periphery of the said hollow fiber membrane module and the said microbubble generation part may be open | released, and the upper and lower sides were opened, and the lower end part of the said wall material widens, A membrane filtration unit, characterized in that it has an extended skirt portion. The film | membrane of Claim 3 whose extension length in the horizontal direction of the said skirt part is 1 mm or more and 1000 mm or less, and the inclination angle with respect to the perpendicular | vertical line extended vertically downward from the lower end part of the said wall material of the said skirt part is 10 degrees or more and 70 degrees or less. Filtration unit.

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